Typhoid fever is a bacterial infection that is spread through the oral-fecal route–usually via polluted water or food.

Mary Mallon, an immigrant from Ireland, is a carrier for typhoid fever when she lands in the U.S. The New York Department of Health claims that Mallon, a domestic cook, is responsible for spreading the disease to over 50 people, resulting in at least 3 deaths.

As an asymptomatic carrier of Salmonella typhi, her nickname of “Typhoid Mary” becomes synonymous with the spread of the disease. After being forced to quarantine by the New York City Department of Health, Mallon is released under the promise never to work in food handling again.

However, Mallon will eventually return to work as a cook, as this is the only work she knows. She will be forced back into quarantine, where she will remain until she eventually dies.

No one will ever explain to Mallon what it means to be an asymptomatic carrier. She will unsuccessfully sue the Health Department and fight against their attempt to have her gallbladder removed.

At the time of her death, 400 other asymptomatic carriers will have been identified, but no one else will be targeted by the Health Department with the same fervor.